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glibc/elf/dl-lookup.c
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/* Look up a symbol in the loaded objects. | |
Copyright (C) 1995-2002, 2003, 2004, 2005 Free Software Foundation, Inc. | |
This file is part of the GNU C Library. | |
The GNU C Library is free software; you can redistribute it and/or | |
modify it under the terms of the GNU Lesser General Public | |
License as published by the Free Software Foundation; either | |
version 2.1 of the License, or (at your option) any later version. | |
The GNU C Library is distributed in the hope that it will be useful, | |
but WITHOUT ANY WARRANTY; without even the implied warranty of | |
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
Lesser General Public License for more details. | |
You should have received a copy of the GNU Lesser General Public | |
License along with the GNU C Library; if not, write to the Free | |
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA | |
02111-1307 USA. */ | |
#include <alloca.h> | |
#include <libintl.h> | |
#include <stdlib.h> | |
#include <string.h> | |
#include <unistd.h> | |
#include <ldsodefs.h> | |
#include <dl-hash.h> | |
#include <dl-machine.h> | |
#include <bits/libc-lock.h> | |
#include <tls.h> | |
#include <assert.h> | |
#define VERSTAG(tag) (DT_NUM + DT_THISPROCNUM + DT_VERSIONTAGIDX (tag)) | |
/* We need this string more than once. */ | |
static const char undefined_msg[] = "undefined symbol: "; | |
struct sym_val | |
{ | |
const ElfW(Sym) *s; | |
struct link_map *m; | |
}; | |
#define make_string(string, rest...) \ | |
({ \ | |
const char *all[] = { string, ## rest }; \ | |
size_t len, cnt; \ | |
char *result, *cp; \ | |
\ | |
len = 1; \ | |
for (cnt = 0; cnt < sizeof (all) / sizeof (all[0]); ++cnt) \ | |
len += strlen (all[cnt]); \ | |
\ | |
cp = result = alloca (len); \ | |
for (cnt = 0; cnt < sizeof (all) / sizeof (all[0]); ++cnt) \ | |
cp = __stpcpy (cp, all[cnt]); \ | |
\ | |
result; \ | |
}) | |
/* Statistics function. */ | |
#ifdef SHARED | |
# define bump_num_relocations() ++GL(dl_num_relocations) | |
#else | |
# define bump_num_relocations() ((void) 0) | |
#endif | |
/* The actual lookup code. */ | |
#include "do-lookup.h" | |
/* Add extra dependency on MAP to UNDEF_MAP. */ | |
static int | |
internal_function | |
add_dependency (struct link_map *undef_map, struct link_map *map) | |
{ | |
struct link_map **list; | |
struct link_map *runp; | |
unsigned int act; | |
unsigned int i; | |
int result = 0; | |
/* Avoid self-references and references to objects which cannot be | |
unloaded anyway. */ | |
if (undef_map == map) | |
return 0; | |
/* Make sure nobody can unload the object while we are at it. */ | |
__rtld_lock_lock_recursive (GL(dl_load_lock)); | |
/* Avoid references to objects which cannot be unloaded anyway. */ | |
if (map->l_type != lt_loaded | |
|| (map->l_flags_1 & DF_1_NODELETE) != 0) | |
goto out; | |
/* If the object with the undefined reference cannot be removed ever | |
just make sure the same is true for the object which contains the | |
definition. */ | |
if (undef_map->l_type != lt_loaded | |
|| (undef_map->l_flags_1 & DF_1_NODELETE) != 0) | |
{ | |
map->l_flags_1 |= DF_1_NODELETE; | |
goto out; | |
} | |
/* Determine whether UNDEF_MAP already has a reference to MAP. First | |
look in the normal dependencies. */ | |
if (undef_map->l_initfini != NULL) | |
{ | |
list = undef_map->l_initfini; | |
for (i = 0; list[i] != NULL; ++i) | |
if (list[i] == map) | |
goto out; | |
} | |
/* No normal dependency. See whether we already had to add it | |
to the special list of dynamic dependencies. */ | |
list = undef_map->l_reldeps; | |
act = undef_map->l_reldepsact; | |
for (i = 0; i < act; ++i) | |
if (list[i] == map) | |
goto out; | |
/* The object is not yet in the dependency list. Before we add | |
it make sure just one more time the object we are about to | |
reference is still available. There is a brief period in | |
which the object could have been removed since we found the | |
definition. */ | |
runp = GL(dl_ns)[undef_map->l_ns]._ns_loaded; | |
while (runp != NULL && runp != map) | |
runp = runp->l_next; | |
if (runp != NULL) | |
{ | |
/* The object is still available. Add the reference now. */ | |
if (__builtin_expect (act >= undef_map->l_reldepsmax, 0)) | |
{ | |
/* Allocate more memory for the dependency list. Since this | |
can never happen during the startup phase we can use | |
`realloc'. */ | |
void *newp; | |
undef_map->l_reldepsmax += 5; | |
newp = realloc (undef_map->l_reldeps, | |
undef_map->l_reldepsmax | |
* sizeof (struct link_map *)); | |
if (__builtin_expect (newp != NULL, 1)) | |
undef_map->l_reldeps = (struct link_map **) newp; | |
else | |
/* Correct the addition. */ | |
undef_map->l_reldepsmax -= 5; | |
} | |
/* If we didn't manage to allocate memory for the list this is | |
no fatal mistake. We simply increment the use counter of the | |
referenced object and don't record the dependencies. This | |
means this increment can never be reverted and the object | |
will never be unloaded. This is semantically the correct | |
behavior. */ | |
if (__builtin_expect (act < undef_map->l_reldepsmax, 1)) | |
undef_map->l_reldeps[undef_map->l_reldepsact++] = map; | |
/* Display information if we are debugging. */ | |
if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_FILES, 0)) | |
_dl_debug_printf ("\ | |
\nfile=%s [%lu]; needed by %s [%lu] (relocation dependency)\n\n", | |
map->l_name[0] ? map->l_name : rtld_progname, | |
map->l_ns, | |
undef_map->l_name[0] | |
? undef_map->l_name : rtld_progname, | |
undef_map->l_ns); | |
} | |
else | |
/* Whoa, that was bad luck. We have to search again. */ | |
result = -1; | |
out: | |
/* Release the lock. */ | |
__rtld_lock_unlock_recursive (GL(dl_load_lock)); | |
return result; | |
} | |
static void | |
internal_function | |
_dl_debug_bindings (const char *undef_name, struct link_map *undef_map, | |
const ElfW(Sym) **ref, struct r_scope_elem *symbol_scope[], | |
struct sym_val *value, | |
const struct r_found_version *version, int type_class, | |
int protected); | |
/* Search loaded objects' symbol tables for a definition of the symbol | |
UNDEF_NAME, perhaps with a requested version for the symbol. */ | |
lookup_t | |
internal_function | |
_dl_lookup_symbol_x (const char *undef_name, struct link_map *undef_map, | |
const ElfW(Sym) **ref, | |
struct r_scope_elem *symbol_scope[], | |
const struct r_found_version *version, | |
int type_class, int flags, struct link_map *skip_map) | |
{ | |
const unsigned long int hash = _dl_elf_hash (undef_name); | |
struct sym_val current_value = { NULL, NULL }; | |
struct r_scope_elem **scope = symbol_scope; | |
bump_num_relocations (); | |
/* No other flag than DL_LOOKUP_ADD_DEPENDENCY is allowed if we look | |
up a versioned symbol. */ | |
assert (version == NULL || flags == 0 || flags == DL_LOOKUP_ADD_DEPENDENCY); | |
size_t i = 0; | |
if (__builtin_expect (skip_map != NULL, 0)) | |
{ | |
/* Search the relevant loaded objects for a definition. */ | |
while ((*scope)->r_list[i] != skip_map) | |
++i; | |
assert (i < (*scope)->r_nlist); | |
} | |
/* Search the relevant loaded objects for a definition. */ | |
for (size_t start = i; *scope != NULL; start = 0, ++scope) | |
{ | |
int res = do_lookup_x (undef_name, hash, *ref, ¤t_value, *scope, | |
start, version, flags, skip_map, type_class); | |
if (res > 0) | |
break; | |
if (__builtin_expect (res, 0) < 0 && skip_map == NULL) | |
{ | |
/* Oh, oh. The file named in the relocation entry does not | |
contain the needed symbol. This code is never reached | |
for unversioned lookups. */ | |
assert (version != NULL); | |
const char *reference_name = undef_map ? undef_map->l_name : NULL; | |
/* XXX We cannot translate the message. */ | |
_dl_signal_cerror (0, (reference_name[0] | |
? reference_name | |
: (rtld_progname ?: "<main program>")), | |
N_("relocation error"), | |
make_string ("symbol ", undef_name, ", version ", | |
version->name, | |
" not defined in file ", | |
version->filename, | |
" with link time reference", | |
res == -2 | |
? " (no version symbols)" : "")); | |
*ref = NULL; | |
return 0; | |
} | |
} | |
if (__builtin_expect (current_value.s == NULL, 0)) | |
{ | |
if ((*ref == NULL || ELFW(ST_BIND) ((*ref)->st_info) != STB_WEAK) | |
&& skip_map == NULL) | |
{ | |
/* We could find no value for a strong reference. */ | |
const char *reference_name = undef_map ? undef_map->l_name : ""; | |
const char *versionstr = version ? ", version " : ""; | |
const char *versionname = (version && version->name | |
? version->name : ""); | |
/* XXX We cannot translate the message. */ | |
_dl_signal_cerror (0, (reference_name[0] | |
? reference_name | |
: (rtld_progname ?: "<main program>")), | |
N_("symbol lookup error"), | |
make_string (undefined_msg, undef_name, | |
versionstr, versionname)); | |
} | |
*ref = NULL; | |
return 0; | |
} | |
int protected = (*ref | |
&& ELFW(ST_VISIBILITY) ((*ref)->st_other) == STV_PROTECTED); | |
if (__builtin_expect (protected != 0, 0)) | |
{ | |
/* It is very tricky. We need to figure out what value to | |
return for the protected symbol. */ | |
if (type_class == ELF_RTYPE_CLASS_PLT) | |
{ | |
if (current_value.s != NULL && current_value.m != undef_map) | |
{ | |
current_value.s = *ref; | |
current_value.m = undef_map; | |
} | |
} | |
else | |
{ | |
struct sym_val protected_value = { NULL, NULL }; | |
for (scope = symbol_scope; *scope != NULL; i = 0, ++scope) | |
if (do_lookup_x (undef_name, hash, *ref, &protected_value, | |
*scope, i, version, flags, skip_map, | |
ELF_RTYPE_CLASS_PLT) != 0) | |
break; | |
if (protected_value.s != NULL && protected_value.m != undef_map) | |
{ | |
current_value.s = *ref; | |
current_value.m = undef_map; | |
} | |
} | |
} | |
/* We have to check whether this would bind UNDEF_MAP to an object | |
in the global scope which was dynamically loaded. In this case | |
we have to prevent the latter from being unloaded unless the | |
UNDEF_MAP object is also unloaded. */ | |
if (__builtin_expect (current_value.m->l_type == lt_loaded, 0) | |
/* Don't do this for explicit lookups as opposed to implicit | |
runtime lookups. */ | |
&& (flags & DL_LOOKUP_ADD_DEPENDENCY) != 0 | |
/* Add UNDEF_MAP to the dependencies. */ | |
&& add_dependency (undef_map, current_value.m) < 0) | |
/* Something went wrong. Perhaps the object we tried to reference | |
was just removed. Try finding another definition. */ | |
return _dl_lookup_symbol_x (undef_name, undef_map, ref, | |
symbol_scope, version, type_class, | |
flags, skip_map); | |
/* The object is used. */ | |
current_value.m->l_used = 1; | |
if (__builtin_expect (GLRO(dl_debug_mask) | |
& (DL_DEBUG_BINDINGS|DL_DEBUG_PRELINK), 0)) | |
_dl_debug_bindings (undef_name, undef_map, ref, symbol_scope, | |
¤t_value, version, type_class, protected); | |
*ref = current_value.s; | |
return LOOKUP_VALUE (current_value.m); | |
} | |
/* Cache the location of MAP's hash table. */ | |
void | |
internal_function | |
_dl_setup_hash (struct link_map *map) | |
{ | |
Elf_Symndx *hash; | |
Elf_Symndx nchain; | |
if (!map->l_info[DT_HASH]) | |
return; | |
hash = (void *) D_PTR (map, l_info[DT_HASH]); | |
map->l_nbuckets = *hash++; | |
nchain = *hash++; | |
map->l_buckets = hash; | |
hash += map->l_nbuckets; | |
map->l_chain = hash; | |
} | |
static void | |
internal_function | |
_dl_debug_bindings (const char *undef_name, struct link_map *undef_map, | |
const ElfW(Sym) **ref, struct r_scope_elem *symbol_scope[], | |
struct sym_val *value, | |
const struct r_found_version *version, int type_class, | |
int protected) | |
{ | |
const char *reference_name = undef_map->l_name; | |
if (GLRO(dl_debug_mask) & DL_DEBUG_BINDINGS) | |
{ | |
_dl_debug_printf ("binding file %s [%lu] to %s [%lu]: %s symbol `%s'", | |
(reference_name[0] | |
? reference_name | |
: (rtld_progname ?: "<main program>")), | |
undef_map->l_ns, | |
value->m->l_name[0] ? value->m->l_name : rtld_progname, | |
value->m->l_ns, | |
protected ? "protected" : "normal", undef_name); | |
if (version) | |
_dl_debug_printf_c (" [%s]\n", version->name); | |
else | |
_dl_debug_printf_c ("\n"); | |
} | |
#ifdef SHARED | |
if (GLRO(dl_debug_mask) & DL_DEBUG_PRELINK) | |
{ | |
int conflict = 0; | |
struct sym_val val = { NULL, NULL }; | |
if ((GLRO(dl_trace_prelink_map) == NULL | |
|| GLRO(dl_trace_prelink_map) == GL(dl_ns)[LM_ID_BASE]._ns_loaded) | |
&& undef_map != GL(dl_ns)[LM_ID_BASE]._ns_loaded) | |
{ | |
const unsigned long int hash = _dl_elf_hash (undef_name); | |
do_lookup_x (undef_name, hash, *ref, &val, | |
undef_map->l_local_scope[0], 0, version, 0, NULL, | |
type_class); | |
if (val.s != value->s || val.m != value->m) | |
conflict = 1; | |
} | |
# ifdef USE_TLS | |
if (value->s | |
&& (__builtin_expect (ELFW(ST_TYPE) (value->s->st_info) | |
== STT_TLS, 0))) | |
type_class = 4; | |
# endif | |
if (conflict | |
|| GLRO(dl_trace_prelink_map) == undef_map | |
|| GLRO(dl_trace_prelink_map) == NULL | |
|| type_class == 4) | |
{ | |
_dl_printf ("%s 0x%0*Zx 0x%0*Zx -> 0x%0*Zx 0x%0*Zx ", | |
conflict ? "conflict" : "lookup", | |
(int) sizeof (ElfW(Addr)) * 2, | |
(size_t) undef_map->l_map_start, | |
(int) sizeof (ElfW(Addr)) * 2, | |
(size_t) (((ElfW(Addr)) *ref) - undef_map->l_map_start), | |
(int) sizeof (ElfW(Addr)) * 2, | |
(size_t) (value->s ? value->m->l_map_start : 0), | |
(int) sizeof (ElfW(Addr)) * 2, | |
(size_t) (value->s ? value->s->st_value : 0)); | |
if (conflict) | |
_dl_printf ("x 0x%0*Zx 0x%0*Zx ", | |
(int) sizeof (ElfW(Addr)) * 2, | |
(size_t) (val.s ? val.m->l_map_start : 0), | |
(int) sizeof (ElfW(Addr)) * 2, | |
(size_t) (val.s ? val.s->st_value : 0)); | |
_dl_printf ("/%x %s\n", type_class, undef_name); | |
} | |
} | |
#endif | |
} |